Changes

In some cases where the underdrain layer has sufficient depth to accommodate it, a larger bore perforated pipe (e.g. ≥ 300 mm) may be used to add further storage capacity. Ultimately this idea may result in the use of retention chambers to create significant reservoir storage beneath a planted area. Be sure to check with manufacturers about the compatability of their systems with [[trees]].

In some cases where the underdrain layer has sufficient depth to accommodate it, a larger bore perforated pipe (e.g. ≥ 300 mm) may be used to add further storage capacity. Ultimately this idea may result in the use of retention chambers to create significant reservoir storage beneath a planted area. Be sure to check with manufacturers about the compatability of their systems with [[trees]].

==Spacing drainage pipes==

===Spacing drainage pipes to reduce groundwater mounding===

[[File:Drain spacing.jpg|thumb|The yellow box represents the recommended hydraulic conductivity of bioretention filter media]]

[[File:Drain spacing.jpg|thumb|The yellow box represents the recommended hydraulic conductivity of bioretention filter media]]

In most LID underdrain applications, lateral drains should be spaced between 5 - 6 m apart.

In most LID underdrain applications, lateral drains should be spaced between 5 - 6 m apart.